Radar systems are well known in the art to detect objects and targets using electromagnetic waves. Traditionally, radio waves or pulses have been transmitted by a radar dish or antenna to bounce off an object in their path. The reflected wave is then returned to a receiver and compared to the initially transmitted wave. Using known methods, the signal reflected from the target to the receiver is used to indicate both the position and/or velocity of the target relative to the transmitter and receiver.
Common radar systems use different methods for directing the transmitted signal (i.e. radar signal) in a desired target direction. Some prior art radar systems have been constructed using mechanically rotating antenna or with mechanical means for directing the radar signal. Other prior art radar systems have been designed using electronically controlled phased arrays which are composed of a group of antennas where the signal transmitted from the antennas are added in phase in such a way that the effective radiation pattern of the array is reinforced in a desired direction of propagation. Radar systems using phased arrays are able to control the angular direction of the radar signal quickly and accurately from a fixed position. Phased array systems also benefit from reduced transmission power requirements for any single antenna, allowing for stronger radar signals from antennae of specific power ratings.
To add the signals from the different antennas in a phased array radar system, different types of phase-shifters are known in the art. Research into micro-electromechanical system (MEMS) based RF switches is being conducted for use in radar systems, as MEMS-based phase-shifters provide low insertion loss, high isolation and fast response time in a small package. However, the circuitry necessary to form a phased array using MEMS-based RF switches can be complicated and the power requirements for such an array may be high.
A Rotman lens is a passive device for beam forming and for directing a radar signal. The design of a Rotman lens was first described by Walter Rotman in U.S. Pat. No. 3,170,158 (the Rotman Patent) and further in U.S. Pat. No. 4,381,509, which are herein incorporated by reference in their entirety. A Rotman lens utilizes the geometry of the lens cavity to adjust the phases of multiple input beams to provide real time beamforming and beam steering without the requirement for Radio Frequency (RF) switch-based phase shifters. Furthermore, as the Rotman lens forms a radar signal by exploiting the physical properties of the lens cavity without any form of microelectronic signal processing, the complexity of the control circuitry required for beamforming is dramatically reduced.
In an exemplary prior art application for motor vehicles, luxury manufacturers such as Mercedes®, BMW®, Lexus®, Jaguar®, Volvo®, and Ford® employ radar systems developed by manufacturers, such as Bosch®, Continental®, Infineon®, SmartMicro®, M/A-Com®, Hitachi® and Fujitsu®. Current radar systems rely upon two distinct radar technologies. Pulsed radars are employed by car manufacturers such as Mercedes®, while Frequency Modulated Continuous Wave (FMCW) radar systems are employed by car manufacturers, such as Jaguar® and BMW®. These prior art systems require mechanical rotation, utilizing an external motor, to scan through the desired field of view. Furthermore, some prior art systems incorporate discrete systems, such as a separate antennae arrays. Often, these prior art systems suffer from corrosion, but also inadequate resolution and range finding for driving at high speeds and the reliability of many prior art systems suffer in difficult driving conditions. Accordingly, there is a need for an improved radar system incorporating an integrated solution to provide superior performance.
Finally, prior art systems requiring mechanical scanning capabilities are subject to wear, tear and thermal drift. Pulsed or FMCW radar systems incorporating mechanical scanning are too expensive to be included in most mid-range or low-end vehicles.
Accordingly, the inventor has appreciated that a low cost collision avoidance and pre-crash warning system will improve highway driving dramatically, if it can be made affordable across a wider spectrum of manufacturers and vehicles. Additional embodiments may be operable in further vehicle types and other applications, including without restriction, robotics, boats, airplanes, toys and security systems.